Blender's garbage collecting isn't ideal in this case. Sometimes it requires to re-save file again to get rid of all unused datablocks. Wouldn't consider this is a bug, it's known behavior.
Not sure why there's no objects creating for this scene, will ask our collada developers to look into this.
Thanks for the report, but collada is currently kind of WIP thing which fails in plenty of cases. so will close report for now.